Producers, suppliers, and consumers of electrical power rely on energy meters to monitor power consumption and quality for numerous purposes, including billing, revenue, power distribution management, and process management. Traditionally, the primary means of measuring power consumption was an electromechanical power meter. A number of other types of meters and equipment measured other parameters of power generation, distribution, usage, and quality. As technology has improved, intelligent electronic devices (IEDs), such as digital power and energy meters, Programmable Logic Controllers (PLCs), electronically-controlled Remote Terminal Units (RTUs), protective relays, fault recorders, and the like, have slowly replaced their electromechanical and analog counterparts.
The shift to using IEDs instead of or in addition to analog and electromechanical devices provides a vast array of advantages including improvements in measurement accuracy (e.g., measurements of voltage, current, power consumption, power quality, etc.) and system control (e.g., allowing a meter to trip a relay or circuit breaker). As a result of the advent of digital metering, a single device can now implement functionality previously implemented in two or more separate devices. Communication enabled by digital processors allows devices to share information with each other, with remote terminals, and even directly with remote users via electronic mail and the World Wide Web.
Some of the functionality resulting from the improvements in technology may be implemented without increasing the number of components, and by extension the size, of the IED. Such is the case, for example, where a single microprocessor may be programmed to perform multiple functions. However, this is not always true. Some of the additional functions included in IEDs require specialized hardware. For example, the inclusion of a specialized communication interface, such as a fiber optic port or an infrared transceiver, requires specialized interface hardware. These and other functions may also require a specialized set of integrated circuits (ICs) (i.e., a chipset) to implement the unique communication protocols required. Moreover, some functions (or combinations of functions) require more processing power than a single processor can deliver, and other functions are more appropriately implemented on a specialized processor that is designed for a particular task or a particular type of processing. Additional processors and specialized hardware necessarily increase the size of the IED.
Despite the pace at which manufacturers release IEDs with new features and functionality, market pressure continues to favor smaller and, of course, less expensive devices. These types of improvements have been hampered because of physical space limitations on a printed circuit board. For example, traditional digital meters utilized Light Emitting Diodes (LEDs) for indication and a display of a user interface. These diodes, among other components were mounted onto a printed circuit board using through-hole technology. Through-hole technology refers to the mounting scheme used for electronic components that involves the use of pins on the components that are inserted into holes drilled in printed circuit boards (PCBs) and soldered to pads on the opposite side of the PCB. While through-hole mounting provides strong mechanical bonds, the additional drilling required makes the board more expensive to produce. It also limits the available routing area for signal traces on layers immediately below the top layer on multilayer boards since the holes must pass through all layers to the opposite side. Furthermore, components mounted by this technique makes it virtual impossible to mount additional components on the opposite side of the board.
Because of these limitations, multiple printed circuit boards needed to be used to support the display in addition to electronics and connectors. Often three or more printed circuit boards were used to support and/or accommodate the needed components. The boards generally included a display board connected to an electronics board using connectors. The electronics board which included a processor was then connected by an additional set of connectors to another board to hold interface connectors, a power supply, communication, etc. Due to the fact that all these connectors were used to connect the boards together, the space on these printed circuit boards was used inefficiently. This made the power meters bulky and large and difficult to retrofit within existing analog enclosures. Therefore, further improvements to intelligent electronic devices are desirable.